from datetime import datetime

kevin = {
    'num':      "10000",
    'name':     "Kevin",
    'gender':   "Male",
    'birthday': datetime(1999, 2, 1),
    'days':     0
}


def calc_living_days(someone):
    gap = datetime.now() - someone['birthday']
    someone['days'] = gap.days


calc_living_days(kevin)
print(kevin['days'])

